A typical receiver of a satellite with multispot coverage and OBP aims at delivering to each on-board demodulator the baseband image of the groups of RF signals received from each spot beam. A conventional RF receiver consists of at least as many input chains as beams and each chain typically includes a low noise amplifier, an automatic gain controller, an input filter, a first down-conversion unit to intermediate frequency with IF amplifier, at least one group filter to filter the incoming signal groups, a second downconversion unit to convert down the selected group of signals to a second intermediate frequency, and an analog-to-digital converter. The receiver possibly includes a switching matrix for switching the signals over the different parallel channels.
The circuitry of such a signal receiver is complex and heavy because the required functions of amplification and conversion to baseband are complicated for the following reasons:
(i) the need of providing frequency conversion for each group of signals in each beam, the need of ensuring a high assignment flexibility which requires several reference frequencies to be provided for the various down conversions depending on the traffic needs and avoiding interferences with adjacent systems; PA0 (ii) the requirement for a complex down conversion scheme, in particular to meet the prescribed phase noise requirements when using several reference frequencies as indicated above; PA0 (iii) the requirement of providing intermediate amplification stages with sophisticated automatic gain controlers, due to the complexity and the large number of devices implied by the above requirements (i) and (ii).